Microstructure, Corrosion Resistance, and Magnetic Properties of LaFe12.35-xCo0.65SixC0.15(x = 1.3, 1.4, 1.5) Compounds after Corrosion in Distilled Water.

Corrosion tests were carried out by immersion the LaFe12.35-xCo0.65SixC0.15(x = 1.3, 1.4, 1.5) compounds in distilled water for different times. The effect of corrosion is systematically studied in terms of morphology, microstructure, corrosion resistance, and magnetic properties. The results show that after 30-min corrosion, obvious corroded spots appeared on the surface of all compounds. It was also found that Si has an adverse effect on corrosion resistance. With the increase of Si content, the corroded spots are connected. The Ecorr decreased from − 0.57 to − 0.65 V while Icorr increased from 3.91 to 5.08 μA/cm2 with increasing the Si content from 1.3 to 1.5. In continuing to extend the corrosion time to 7 days, a large-scale corrosion area appeared, accompanied by the peeling of the main phase as anode and the retention of α-Fe phase as cathode. Meanwhile, the magnetic entropy change of LaFe10.95Co0.65Si1.4C0.15 compounds decreased from 8.1 to 7.7 J/(kg K) when the corrosion time increased from 0 to 7 days. After 21-day corrosion, the sample surface was completely covered by corrosion products. Furthermore, long-time corrosion has a significant effect on magnetic properties. The Curie temperature increased from 289 to 314 K for 0-day and 21-day corrosion of LaFe10.95Co0.65Si1.4C0.15 compounds, respectively. Significantly, the magnetic entropy change curves showed two peaks in theΔS-Tc curves. Magnetic stability was decreased after long-time corrosion. [ABSTRACT FROM AUTHOR]